1. Related Application
The assignee of the present invention is also the assignee of the following design patent application on the housing containing the present invention: "Solar Powered Light Housing", filed June 22, 1984, Ser. No. 623,378, Dennis R. Schlepp.
2. Field of the Invention
The present invention relates to remote solar powered devices and, more particularly, to solar powered lights and lamps that are automatically synchronized with the rising and the setting of the sun to track seasonal variations.
3. Discussion of Prior Art
A need exists in remote and rural locations for solar powered devices, such as lamps, that provide high illumination with excellent battery reliability.
Prior to the present application, a patentability investigation for such devices was performed in which the following prior art approaches were uncovered:
______________________________________ Inventor U.S. Pat. No. Issue Date ______________________________________ M. E. Paradise 2,889,490 June 2, 1959 J. J. Coleman 2,901,669 Aug. 25, 1959 H. G. Zinsmeyer 3,428,861 Feb. 18, 1969 Katsumi Takeda 3,231,747 Jan. 25, 1966 L. J. Woodward 3,240,960 March 15, 1966 G. W. Bowers 3,317,809 May 2, 1967 H. T. Adkins 3,351,762 Nov. 7, 1967 P. R. Corn 3,529,214 Sept. 15, 1970 Frank M. Olin 3,599,048 Aug. 10, 1971 Art Lee 3,673,413 June 27, 1972 Ezra Schacht 3,789,220 Jan. 29, 1974 George Duve 3,916,183 Oct. 28, 1975 John J. Powers 3,995,202 Nov. 30, 1976 De Avila-Serafin 4,008,415 Feb. 15, 1977 Earle W. Kazis 4,009,051 Feb. 22, 1977 Chapdelaine 4,177,405 Dec. 4, 1979 Egon H. Elssner 4,198,563 Apr. 15, 1980 Robert Membreno 4,209,728 June 24, 1980 Aksel Jespersen 4,213,062 July 15, 1980 Victor Sansum 4,237,377 Dec. 2, 1980 William Rogers 4,314,198 Feb. 2, 1982 John K. Grady 4,362,970 Dec. 7, 1982 ______________________________________
In the Sansum patent a sun-synchronized timer is set forth for use with a photoelectric lamp control circuit. The electric lamp is connected, at dusk, each evening and is disconnected a predetermined time later. The predetermined time starts with the dawn and produces a series of electrical timing pulses which enter a binary counter. The output of the binary counter is digitally compared with preset time values in an encoder and when the comparison is identical, a signal is generated to an output latch for deactivating the load and resetting the circuit. The user can encode whatever predetermined time he desires. Hence, the Sansum circuit is synchronized each day with the time of day.
The patent to Duve et al relates to a mechanical control unit which measures the span of time between dawn and dusk for each day. Based upon the "span of time" determination, a timer operates for a period of time after dusk. The period of time being longer when the span of time is shorter and shorter when the span of time is longer. Hence, the load which is turned on at dusk at deactivated at substantially the same time (for example midnight) each night, even though the length of time that the load is on varies with the seasons.
The Schacht patent relates to a light sensitive electrical timing circuit which causes a timer to become activated at dawn and to deactivate a load which was turned on at dusk a predetermined amount of time after dawn such as sixteen hours. Additionally, a compensation time circuit is provided for compensating seasonal changes so that the load is deactivated approximately the same time each night. The Schacht circuit utilizes bi-metal controls and mechanical timers to perform its operation.
The patent issued to Rogers uses a solar power source for its lighting system. The Rogers device is designed to be the power source for a low voltage solar light comprised of photovoltaic panels. At dusk, the system operates to turn the load on and an electronic timer is activated which generates a series of pulses into a binary counter which after a predetermined time deactivates the load.
The Woodward patent relates to a photoelectric lighting control which turns on a load at dusk and then turns it off a predetermined time later. With the rising of the next dawn, the timer is reset, but does not commence timing until dusk is again sensed.
Takeda et al teaches the use of a photoelectric self-correcting timing device for activating electric loads. The Takeda device being mechanical is designed to become activated each dawn and then to go through a mechanical process of revolution to compensate for the variations in the seasonal rising and setting of the sun.
The Grady patent relates to the provision of two timers interacting with each other and both being started at dusk to control street lamps or other loads including household hot water heaters. The first time frame is generated with the light change and at the end of the first time frame, the load is turned on or off. A second time frame which is longer than the first time frame is then used to turn the loads off.
The patent issued to Membreno relates to an outdoor lighting system and method wherein pulse shaping, counting, and reset circuits generate a first time frame commencing at dusk, the timing out of which, causes the load to become deactivated. The provision of a second time frame longer than the first, which when it times out, may cause the load to become activated, if it is still dark outside.
The Elssner patent relates to circuits similar to that of Membreno in that an electronic control circuit is provided which provides a timer activated at dusk to turn off an activated load after a predetermined time has elapsed. A "hold off" time interval is then provided as an override to prevent the photo detector from becoming activated for the hold off period of time.
In the patent issued to De Avila-Serafin et al a photo control for electric lamps is set forth wherein, at dusk, the load becomes activated and is turned off after a predetermined period of time. The predetermined period of time is determined by digitally counting pulses from an oscillator and determining the count to a predetermined value. When the predetermined count is reached, the circuit acts to turn the load off. The frequency of the pulses from the oscillator are changed according to the outside temperature to change the predetermined period of time based upon summer and winter conditions.
Zinsmeyer teaches the use of a photo electric timer control which causes a load to turn on a predetermined time before dawn and also a predetermined time after dusk. The circuit is electronic and can be modified so that the load is only turned on after dusk, only before dawn, or before dawn and after dusk. The predetermined time intervals can be adjusted by adjusting the potentiometer.
None of these prior art approaches sets forth the present invention, as wholly constituted, which provides a circuit which senses the prior dawn and counts down for a predetermined time interval to turn the light on for a predetermined period of time just before dawn of the next day. In addition, when dusk is sensed, a separate timer is provided which becomes activated to time out a predetermined time later. In addition, the present invention provides the detection of the ambient solar level by means of the solar array itself. The present invention further contemplates the use of a single control for adjusting three separate potentiometers so that certain parameters are met wherein the amount of time for turning the light on just before sunrise or after sunset can be varied but will always equal a predetermined fixed amount so as not to provide undue discharge of the battery. And finally, provision is made for monitoring the charge on the battery and for deactivating the lamp circuitry should the charge in the battery drop below a predetermined value.